fix(docx): take what a spacer's line and a taller paragraph reach past their block out of the space below

[DemchaAV]

Why

Two things reach past their block in Word, and neither was taken out of the space below it or
named: what followed stood lower than the page sets it, silently.

• A spacer shorter than its line. A spacer in the flow is written as an empty paragraph a
  tenth of a point tall, its height less that tenth owed below it. A spacer of no height — a width
  anchor, as Panel's and PanelLetter's cards open with — kept the whole tenth: every card stood
  that much taller in Word.
• A paragraph whose lines Word sets taller than the page. Word sets every line of a paragraph at
  one height; for lines in more than one size the export writes the tallest line's, and the page
  sets each line at its own, so a wrapped line after a large first one stands closer on the page.
  What a paragraph fell short of the page was owed below it; what it passed the page by was
  not. CompactMono's skills, two lines to a paragraph and each written 0.12pt taller than the
  page, ended its sidebar a point low in Word.

What changed

All in DocxSemanticBackend:

• writeSpacer: a spacer shorter than its hairline leaves the rest of that tenth as
  hangingBelow — the mechanism a line held to its icon already uses. The next block takes it out
  of the space owed above it, then out of its own top edge, and names what is left (space above). Ending a cell, the space the cell owes below takes it first, then the cell's overhang,
  which a row or a panel takes (its padding below). The spacer is still written, so a band, a
  layer column or a shape container measures and writes it as before.
• settleTheLinesWithThePage (was oweWhatTheLinesFallShort): a paragraph whose written lines
  pass the page by more than a tenth of a point hangs that below itself the same way.
• LINES_ROUNDING_TOLERANCE = 0.1pt both ways. Measured: Word sets baselines on a grid 0.12pt
  (1/600in) apart — a 194-twip exact line steps 9.72pt six times and 9.60 once — so a correction
  under a tenth of a point moves a line a step or nothing: at 0.01pt, 13 documents moved nearer the
  page in Word and 13 further. Past that, the two directions are measured, not assumed:
  • lines rounded up to the twip, over enough of them, hang: OrangeOps' achievement lines, a
    0.08pt gap between them written as a tenth, and SlateOrange's profile stand nearer the page
    in Word with it (median 0.29 → 0.22pt and 0.48 → 0.40pt; without it, as on 2.5-dev);
  • what rounding takes from a paragraph written at its tallest line is still not owed (the
    lineIsNotTheTallest gate stays): owed, it stood the lines below ModernInvoice's parties a
    grid step or two lower, and four other documents further from the page.
• holdAParagraphsTopEdgeOnItsPage, leaveThePageAbove and a spacer opening a page now name
  what a block on the page above never took (nameAHangLeftOver) before they forget the hang, pull
  and border below it — and the paragraph one forgets them before its early return for a paragraph
  with no top edge to hold, which used to leave the hang to be named, falsely, on the next page.

Docs: the recipe's Spacers and Line height rows, the "A spacer is its height alone" paragraph and
the one on text running past a block's foot; CHANGELOG.md (v2.5.0).

Verification

• ./mvnw -B -ntp clean verify → BUILD SUCCESS: render-docx 1318 run, 0 failures, 1
  skipped (+11), qa 1820, core 818.
• DocxLineSurplusTest (7): the space below takes a taller paragraph's surplus; what it cannot
  take is named; a paragraph ending a page leaves it there; what a list item ending a page never
  took is named there; the space below takes what a one-size paragraph's rounding adds; a paragraph
  written at its tallest line owes nothing for what its rounding takes; a spacer of no height with
  no space below it is named. DocxContainerSpacingTest (+3): the spacer in the flow, opening a
  card, and ending a padded card (its padding below takes the tenth). DocxSpaceAboveOnANewPageTest
  (+1): a spacer of no height opening a page holds the gap in its line, and the block after it
  takes the tenth.
• Six sabotages, each caught by its own test: the spacer's hang dropped (five tests), the
  paragraph's surplus dropped (four), the shortfall's gate dropped so rounding is owed, the reset
  moved back after the page-top return, rounding's surplus left, the page-top leftover forgotten
  unnamed.
• DOCX fidelity corpus: 9 of 62 documents change, and the report names nothing more (969 notes,
  as on 2.5-dev). Word baseline (word-windows*.tsv, via scripts/docx-visual/word-fidelity.ps1 -Update): all 9 nearer the page in median — cv-panel 0.83 → 0.46pt, cv-compact_mono p90
  0.91 → 0.36pt (its sidebar's foot from about +0.95pt to −0.05pt), cv-nordic_clean 0.23 → 0.16,
  cv-monogram_sidebar 0.28 → 0.20, cv-orange_ops 0.29 → 0.22, cv-slate_orange 0.48 → 0.40;
  letter-panel 0.16 → 0.14 in median, further in its p90 (0.21 → 0.29pt, below). LibreOffice on
  Windows (libreoffice-windows*.tsv): 7 nearer, cv-orange_ops unchanged, letter-panel 0.13 →
  0.19pt. LibreOffice on Linux (libreoffice-linux*.tsv, from CI's docx-fidelity artifact): 7
  nearer — cv-orange_ops 0.26 → 0.18pt among them — and letter-panel 0.13 → 0.19pt, as on
  Windows.

Notes for review

• letter-panel's text now starts where the page sets its card; what is left is how far both
  editors seat its body text off the page's baseline in an exact line — 0.12pt higher in Word, as
  in LibreOffice — a separate defect.
• Places that still drop a hang without naming it, each for a line held to its icon already and
  now for these two sources too, left for their own change: a band's later layer and a layer
  column resuming after another (resumeHere); a band's foot; a composed table cell or a layer
  column, whose cell overhang nothing reads; and a block other than a paragraph, a panel, a table,
  a row, a band or a spacer that the layout opens a page with — a list, a line pair, a picture —
  which takes the hang from the page above and names it falsely.

Lane: shared-engine (DOCX backend) — render-docx only, no public API.